Automatic fire extinguisher for a storage tank with flammable contents

ABSTRACT

A fire extinguisher for a storage tank having a roof movably sealed at edges of the roof to walls of the tank has reservoirs for fire extinguishing fluid on the roof. Each reservoir is connected to a different extinguishing fluid distribution pipe extending along at least part of the sealed roof edge and wall and having heat operated sprinklers spaced along its length to define a section of the fire extinguisher which is supplied with extinguishing fluid from the connected one of the reservoirs. The sections at least partly overlap and the sprinklers in a section part overlapping another have higher operating temperatures than the sprinklers of the other section to sequentially operate the sprinklers in response to heat from a fire whereby the quantity and time during which fire extinguishing fluid is available is extended by first discharging the fluid from the reservoir connected to the section having sprinklers of lower operating temperature and then discharging fluid from the reservoir connected to the section having sprinklers of higher operating temperature.

United States Patent De Boer [75] Inventor: Jan A. De Boer, Hoeven,

Netherlands [73] Assignee: Saval B.V., Breda, Netherlands [22] Filed: Feb. 25, 1974 [21] Appl. No.: 445,565

[30] Foreign Application Priority Data Feb. 27, 1973 Netherlands 7302725 [52] US. Cl. 169/66; 169/16; 169/26 [51] Int. Cl. A62c 35/54 [58] Field of Search 169/46, 66, 67, 68, 37, 169/16, 26

[56] References Cited UNITED STATES PATENTS 3,684,019 8/1972 Emmons et a1. 169/47 3,702,159 11/1972 Livingston 169/37 X 3,741,309 6/1973 McCulloch 169/26 X [451 July 29, 1975 Primary ExaminerM. Henson Wood, .lr. Assistant ExaminerMichael Mar Attorney, Agent, 0r.Fir'm-Brumbaugh, Graves, Donohue & Raymond [57] ABSTRACT A fire extinguisher for a storage tank having a roof movably sealed at edges of the roof to walls of the tank has reservoirs for fire extinguishing fluid on the roof. Each reservoir is connected to a different extinguishing fluid distribution pipe extending along at least part of the sealed roof'edge and wall and having heat operated sprinklers spaced along its length to define a section of the fire extinguisher which is supplied with extinguishing fluid from the connected one of the reservoirs. The sections at least partly overlap and the sprinklers in a section part overlapping another have higher operating temperatures than the sprinklers of the other section to sequentially operate the sprinklers in response to heat from a fire whereby the quantity and time during which-fire extinguishing fluid is available is extended by fi'rst discharging the fluid from the reservoir connected tofthe section having sprinklers of lower operating temperature and then discharging fluid from the reservoir connected to the section having sprinklers of higher operating temperature.

4 Claims, 2 Drawing Figures PATENTEI] JUL 2 9 I975 SHEET AUTOMATIC FIRE EXTINGUISI-IER FOR A STORAGE TANK WITH FLAMMABLE CONTENTS BACKGROUND OF THE INVENTION The present invention relates to a fire extinguisher for a storage tank with flammable contents, said tank comprising a roof with a sealing means between a wall of the tank and an edge of the roof, said roof being movable relative to said wall, and on said roof a number of reservoirs with fire-extinguishing fluid have been arranged, said reservoirs each being connected to sprinklers or sprayers, for example by a fireextinguishing pipe, said sprinklers being kept closed by means of thermo-sensitive elements, said section covering part of the circumference of the roof edge. Fireextinguishing equipment of this kind is generally known. It is customary with large fuel tanks to use a floating roof in order to give as little room as is possible for gas or fumes between the liquid surface and the roof, and, thereby, reduce the chance of having an inflammable mixture develop. This roof with up and down movement is sealed relative to the wall of the cylindrical reservoir.

However, as there is a danger that such a sealing may leak at some places, which involves the risk that a local fire might break out in that region, which might spread over the whole tank, it has been known for some time to place a number of reservoirs with fire-extinguishing fluid on the roof, said reservoirs with an extinguishing pipe and sprinklers covering each a part of the circumference. As fireextinguishing fluid, it is preferred to use bromochlorodi fluor methane, generally known as BCF or halon 121].

If a local fire breaks out at the edge of the roof of a tank, then the sprinkler nearest the fire will come into action, as a result of which the fire will be extinguished by the gas which evolves.

A disadvantage of this known fire extinguisher is that it does not have a reserve supply. For when the reservoir is nearly or entirely empty after extinguishing a fire, the extinguishing equipment is not capable of performing its task effectively when a new fire breaks out in the same section or when the same fire, previously extinguished, starts again.

SUMMARY OF THE INVENTION The object of the invention is to provide a solution and in accordance with the invention, said object is achieved in that the sections overlap each other and that at the region of the overlapping the sprinklers in the one section have a higher operating temperature than the sprinklers in the other section. With the present invention it is achieved that a double fireextinguishing pipe is present along the entire circumference of the edge of the tank, each pipe of said double fire-extinguishing means being connected to an individual reservoir with fire-extinguishing fluid and in which due to the difference in operating temperature during the break out of a fire only one pipe will come into action. i.e. the one in which the sprinklers with the lowest operating temperature are present. So when a fire breaks out, the sprinkler with the lowest operating temperature present at that region will come into action and fight the fire and, in addition, have a cooling effect on the sprinkler with the higher operating temperature. Only when the section put into operation becomes exhausted and the fire is still not extinguished or starts again while the section that has been in operation is exhaused, the temperature near the sprinkler that has been in action will rise further and will reach the operating temperature of the sprinkler of the overlapping section, which section will then come into action with the advantage that it has available the full capacity of the reservoir of the other section.

The difference in operating temperature is necessary in order to assure that the sprinklers of the overlapping sections will not come into action all at the same time, since the reserve supply will then be wasted.

In this connection, it is desirable in accordance with the invention that approximately in the centre between those parts of the sections overlapping each other where the operating temperature of the sprinklers varies, a sprinkler is present in one section, said sprinkler having a still higher operating temperature. If one does not include this sprinkler, then there is the risk that two sprinklers opposite or near to each other, will have the same operating temperature or that with a fire in a region between successive sprinklers a sprinkler is present on either side of the fire in each one of theoverlapping sections with the same operating temperature, so that both sections may again come into action. By assuring that at this region at least one sprinkler has a still higher operating temperature, oneassures that when a fire breaks out in this region the sprinkler with the lowest operating temperature in that region will come into action and that the second sprinkler and extinguisher section will act as a reserve.

In accordance with the invention this may be improved further in that on either side of the sprinkler with the highest operating temperature in the section parts with the sprinklers with the lowest operating temperature, a sprinkler is present which operates between said sprinkler with the highest operating temperature and the next sprinkler with the lowest operating temperature, whereupon the operating temperature lies between the lowest and the highest operating temperature.

The sprinklers of the overlapping sections are preferably arranged right next to each other in order to assure that the sprinkler with the lower operating temperature cools the one with the higher operating temperature.-

Although it is known that one sprinkler can cool the other, sprinklers in known sprinkler installations are generally positioned in such a way that they cannot cool each other.

DESCRIPTION OF THE DRAWINGS The invention will now be described more in detail with reference to the accompanying drawings, wherein:

FIG. 1 illustrates diagrammatically a perspective view of a tank with a known fire extinguisher; and

FIG. 2 is a diagrammatic plan view of the fire extinguisher in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a tank I, such as an oil storage tank or the like, with a floating roof 2. Three reservoirs 3, 4 and 5 with fire-extinguishing fluid, such as BCF, are positioned on said roof, each reservoir being separately connected to an extinguishing pipe 6, 7 and 8 respectively and each pipe having sprinklers 9. Each reservoir containing fire-extinguishing fluid is provided in a known manner with the necessary control and fire alarm equipment.

The arrangement shown in FIG, 1 clearly illustrates that when in one section, for instance in section 7 a fire has broken out and has been extinguished, no further extinguishing is possible in the whole region covered by section 7.

FIG. 2 shows the installation in accordance with the invention with two reservoirs for fire-extinguishing fluid 10 and 11 respectively. However, it is evident that also more than two reservoirs are possible. An extinguishing pipe 12, 13 runs from each reservoir 10 and 11 respectively, each said pipe extending almost to the nearest reservoir to define a section. These pipes have sprinklers and it can be seen clearly that the pipe defined sections overlap each other. The sprinklers have been indicated in the drawing by small circles, the black circles 14 refer to a sprinkler with an operating temperature of for instance 70, the white circles 15 refer to a sprinkler with an operating temperature of for instance 140 and the circles 16 provided with a cross refer to a sprinkler with an operating temperature of for instance 240. Adjacent a last of several successive sprinklers 14 one sprinkler has been indicated by reference numeral 18, said sprinkler 18 having a slightly higher operating temperature than the sprinklers 14 (70), for instance 90.

It will be clear that when a fire breaks out near the sprinklers, the sprinkler or sprinklers with the lowest operating temperature will open to extinguish the fire and keep adjacent sprinklers having higher operating temperatures cooled below their operating temperature. Only when the temperature of the sprinklers further increases, as when the fire breaks out again after the supply of fire-extinguishing fluid from the reservoir connected to the sprinkler with the lowest operating temperature is exhausted and, thereby, the operating temperature of the other sprinklers is reached, will the sprinklers operating at higher temperatures in the section overlapping that of the sprinkler which operated at the lowest temperature sequentially come into action, as a result of which the capacity of extinguishing is increased by approximately 100 percent.

Each section of a fire-extinguishing pipe has a centre distance, such as indicated at reference numeral 17, where the sprinkler with the high operating temperature takes over from the sprinkler with the low operating temperature. Inasmuch as these transitions take place in opposite direction there is a risk without special precautions being taken that even if sprinklers with different operating temperatures lie next to each other, sprinklers with the same operating temperature and, therewith, with the lowest operating temperature are yet too close to each other. If, for instance, in the area indicated by reference numeral 17 a fire broke out and the nearest sprinkler 16 were of the type of sprinkler 14, then both pipes 12 and 13 would come into action, the consequence of which would be that then the sprinklers with the higher operating temperature, indicated by reference numeral 15, would be useless. In order to prevent this operation, sprinkler 16 with the much higher operating temperature has been provided. Said sprinkler will assure that with a fire in the area 17 only the nearest sprinkler 14 (pipe 12) can come into action. Sprinkler 16 in pipe 12 then no longer has significance but sprinkler 15 in pipe 13 certainly has. It is also possible to avoid this problem by omitting the sprinkler indicated by reference numeral 16. However, one does not have a reserve then when a fire breaks out again in the area of sprinkler 16 as one could in an embodiment (not shown) in which the sprinkler l6 nearest area 17 were connected to a fire-extinguishing fluid distribution pipe section other than pipe section 12. Moreover, safety demands that a sprinkler be provided at the re gion of the illustrated sprinkler 16, but in order to guarantee the correct sequence of operation it must be one with a higher operating temperature than the sprinklers l4 and 15.

The sprinklers indicated by reference numeral 18 have an intermediate operating temperature, slightly higher than the lowest, but lower than the higher and highest, for example and lie between sprinklers with the lowest and the highest operating temperatures. This is advisable in order to prevent a fire in the area of a sprinkler 16 from bringing both sections into action by radiation.

1 claim:

1. A fire extinguisher for a storage tank with flammable contents, said tank comprising a roof movable relative to a wall, and said extinguisher comprising a number of reservoirs with fire-extinguishing fluid arranged on said roof, said reservoirs each being connected to a fire-extinguishing pipe provided with heat operated sprinklers for defining a section, said section covering part of the edge of the roof, and chracterized in that said sections overlap each other and that the sprinklers in the overlapping part of said one section have a higher operating temperature than the sprinklers in said other section for first operating the sprinklers in said other section to the exhaustion of said fireextinguishing fluid in said connected reservoir and then operating the sprinklers in said one section.

2. A fire extinguisher in accordance with claim 1, characterized in that in said sections overlapping each other, and where the operating temperature of the sprinklers in said other section changes, a sprinkler in said one section has a highest operating temperature.

3. A fire extinguisher in accordance with claim 2 wherein a sprinkler with an intermediate operating temperature lies between said sprinkler with the highest operating temperature and said sprinkler with the lower operating temperature in each section.

4. Fire extinguisher in accordance with claim 1, characterized in that the sprinklers of the one section have been positioned right next to the sprinklers of the other section. 

1. A fire extinguisher for a storage tank with flammable contents, said tank comprising a roof movable relative to a wall, and said extinguisher comprising a number of reservoirs with fire-extinguishing fluid arranged on said roof, said reservoirs each being connected to a fire-extinguishing pipe provided with heat operated sprinklers for defining a section, said section covering part of the edge of the roof, and chracterized in that said sections overlap each other and that the sprinklers in the overlapping part of said one section have a higher operating temperature than the sprinklers in said other section for first operating the sprinklers in said other section to the exhaustion of said fireextinguishing fluid in said connected reservoir and then operating the sprinklers in said one section.
 2. A fire extinguisher in accordance with claim 1, characterized in that in said sections overlapping each other, and where the operating temperature of the sprinklers in said other section changes, a sprinkler in said one section has a highest operating temperature.
 3. A fire extinguisher in accordance with claim 2 wherein a sprinkler with an intermediate operating temperature lies between said sprinkler with the highest operating temperature and said sprinkler with the lower operating temperature in each section.
 4. Fire extinguisher in accordance with claim 1, characterized in that the sprinklers of the one section have been positioned right next to the sprinklers of the other section. 